liblttng-ust/lttng-events.c

   1 /*
   2  * lttng-events.c
   3  *
   4  * Holds LTTng per-session event registry.
   5  *
   6  * Copyright (C) 2010-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   7  *
   8  * This library is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; only
  11  * version 2.1 of the License.
  12  *
  13  * This library is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with this library; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 #define _GNU_SOURCE
  24 #include <stdio.h>
  25 #include <urcu/list.h>
  26 #include <urcu/hlist.h>
  27 #include <pthread.h>
  28 #include <errno.h>
  29 #include <sys/shm.h>
  30 #include <sys/ipc.h>
  31 #include <stdint.h>
  32 #include <stddef.h>
  33 #include <inttypes.h>
  34 #include <time.h>
  35 #include <lttng/ust-endian.h>
  36 #include "clock.h"
  37
  38 #include <urcu-bp.h>
  39 #include <urcu/compiler.h>
  40 #include <urcu/uatomic.h>
  41 #include <urcu/arch.h>
  42
  43 #include <lttng/tracepoint.h>
  44 #include <lttng/ust-events.h>
  45
  46 #include <usterr-signal-safe.h>
  47 #include <helper.h>
  48 #include <lttng/ust-ctl.h>
  49 #include <ust-comm.h>
  50 #include "error.h"
  51 #include "compat.h"
  52 #include "lttng-ust-uuid.h"
  53
  54 #include "tracepoint-internal.h"
  55 #include "lttng-tracer.h"
  56 #include "lttng-tracer-core.h"
  57 #include "lttng-ust-baddr.h"
  58 #include "wait.h"
  59 #include "../libringbuffer/shm.h"
  60 #include "jhash.h"
  61
  62 /*
  63  * All operations within this file are called by the communication
  64  * thread, under ust_lock protection.
  65  */
  66
  67 static CDS_LIST_HEAD(sessions);
  68
  69 struct cds_list_head *_lttng_get_sessions(void)
  70 {
  71         return &sessions;
  72 }
  73
  74 static void _lttng_event_destroy(struct lttng_event *event);
  75
  76 static
  77 void lttng_session_lazy_sync_enablers(struct lttng_session *session);
  78 static
  79 void lttng_session_sync_enablers(struct lttng_session *session);
  80 static
  81 void lttng_enabler_destroy(struct lttng_enabler *enabler);
  82
  83 /*
  84  * Called with ust lock held.
  85  */
  86 int lttng_session_active(void)
  87 {
  88         struct lttng_session *iter;
  89
  90         cds_list_for_each_entry(iter, &sessions, node) {
  91                 if (iter->active)
  92                         return 1;
  93         }
  94         return 0;
  95 }
  96
  97 static
  98 int lttng_loglevel_match(int loglevel,
  99                 unsigned int has_loglevel,
 100                 enum lttng_ust_loglevel_type req_type,
 101                 int req_loglevel)
 102 {
 103         if (!has_loglevel)
 104                 loglevel = TRACE_DEFAULT;
 105         switch (req_type) {
 106         case LTTNG_UST_LOGLEVEL_RANGE:
 107                 if (loglevel <= req_loglevel || req_loglevel == -1)
 108                         return 1;
 109                 else
 110                         return 0;
 111         case LTTNG_UST_LOGLEVEL_SINGLE:
 112                 if (loglevel == req_loglevel || req_loglevel == -1)
 113                         return 1;
 114                 else
 115                         return 0;
 116         case LTTNG_UST_LOGLEVEL_ALL:
 117         default:
 118                 return 1;
 119         }
 120 }
 121
 122 void synchronize_trace(void)
 123 {
 124         synchronize_rcu();
 125 }
 126
 127 struct lttng_session *lttng_session_create(void)
 128 {
 129         struct lttng_session *session;
 130         int i;
 131
 132         session = zmalloc(sizeof(struct lttng_session));
 133         if (!session)
 134                 return NULL;
 135         CDS_INIT_LIST_HEAD(&session->chan_head);
 136         CDS_INIT_LIST_HEAD(&session->events_head);
 137         CDS_INIT_LIST_HEAD(&session->enablers_head);
 138         for (i = 0; i < LTTNG_UST_EVENT_HT_SIZE; i++)
 139                 CDS_INIT_HLIST_HEAD(&session->events_ht.table[i]);
 140         cds_list_add(&session->node, &sessions);
 141         return session;
 142 }
 143
 144 /*
 145  * Only used internally at session destruction.
 146  */
 147 static
 148 void _lttng_channel_unmap(struct lttng_channel *lttng_chan)
 149 {
 150         struct channel *chan;
 151         struct lttng_ust_shm_handle *handle;
 152
 153         cds_list_del(&lttng_chan->node);
 154         lttng_destroy_context(lttng_chan->ctx);
 155         chan = lttng_chan->chan;
 156         handle = lttng_chan->handle;
 157         /*
 158          * note: lttng_chan is private data contained within handle. It
 159          * will be freed along with the handle.
 160          */
 161         channel_destroy(chan, handle, 0);
 162 }
 163
 164 static
 165 void register_event(struct lttng_event *event)
 166 {
 167         int ret;
 168         const struct lttng_event_desc *desc;
 169
 170         assert(event->registered == 0);
 171         desc = event->desc;
 172         ret = __tracepoint_probe_register(desc->name,
 173                         desc->probe_callback,
 174                         event, desc->signature);
 175         WARN_ON_ONCE(ret);
 176         if (!ret)
 177                 event->registered = 1;
 178 }
 179
 180 static
 181 void unregister_event(struct lttng_event *event)
 182 {
 183         int ret;
 184         const struct lttng_event_desc *desc;
 185
 186         assert(event->registered == 1);
 187         desc = event->desc;
 188         ret = __tracepoint_probe_unregister(desc->name,
 189                         desc->probe_callback,
 190                         event);
 191         WARN_ON_ONCE(ret);
 192         if (!ret)
 193                 event->registered = 0;
 194 }
 195
 196 /*
 197  * Only used internally at session destruction.
 198  */
 199 static
 200 void _lttng_event_unregister(struct lttng_event *event)
 201 {
 202         if (event->registered)
 203                 unregister_event(event);
 204 }
 205
 206 void lttng_session_destroy(struct lttng_session *session)
 207 {
 208         struct lttng_channel *chan, *tmpchan;
 209         struct lttng_event *event, *tmpevent;
 210         struct lttng_enabler *enabler, *tmpenabler;
 211
 212         CMM_ACCESS_ONCE(session->active) = 0;
 213         cds_list_for_each_entry(event, &session->events_head, node) {
 214                 _lttng_event_unregister(event);
 215         }
 216         synchronize_trace();    /* Wait for in-flight events to complete */
 217         cds_list_for_each_entry_safe(enabler, tmpenabler,
 218                         &session->enablers_head, node)
 219                 lttng_enabler_destroy(enabler);
 220         cds_list_for_each_entry_safe(event, tmpevent,
 221                         &session->events_head, node)
 222                 _lttng_event_destroy(event);
 223         cds_list_for_each_entry_safe(chan, tmpchan, &session->chan_head, node)
 224                 _lttng_channel_unmap(chan);
 225         cds_list_del(&session->node);
 226         free(session);
 227 }
 228
 229 int lttng_session_enable(struct lttng_session *session)
 230 {
 231         int ret = 0;
 232         struct lttng_channel *chan;
 233         int notify_socket;
 234
 235         if (session->active) {
 236                 ret = -EBUSY;
 237                 goto end;
 238         }
 239
 240         notify_socket = lttng_get_notify_socket(session->owner);
 241         if (notify_socket < 0)
 242                 return notify_socket;
 243
 244         /* Set transient enabler state to "enabled" */
 245         session->tstate = 1;
 246         /* We need to sync enablers with session before activation. */
 247         lttng_session_sync_enablers(session);
 248
 249         /*
 250          * Snapshot the number of events per channel to know the type of header
 251          * we need to use.
 252          */
 253         cds_list_for_each_entry(chan, &session->chan_head, node) {
 254                 const struct lttng_ctx *ctx;
 255                 const struct lttng_ctx_field *fields = NULL;
 256                 size_t nr_fields = 0;
 257                 uint32_t chan_id;
 258
 259                 /* don't change it if session stop/restart */
 260                 if (chan->header_type)
 261                         continue;
 262                 ctx = chan->ctx;
 263                 if (ctx) {
 264                         nr_fields = ctx->nr_fields;
 265                         fields = ctx->fields;
 266                 }
 267                 ret = ustcomm_register_channel(notify_socket,
 268                         session->objd,
 269                         chan->objd,
 270                         nr_fields,
 271                         fields,
 272                         &chan_id,
 273                         &chan->header_type);
 274                 if (ret) {
 275                         DBG("Error (%d) registering channel to sessiond", ret);
 276                         return ret;
 277                 }
 278                 if (chan_id != chan->id) {
 279                         DBG("Error: channel registration id (%u) does not match id assigned at creation (%u)",
 280                                 chan_id, chan->id);
 281                         return -EINVAL;
 282                 }
 283         }
 284
 285         /* Set atomically the state to "active" */
 286         CMM_ACCESS_ONCE(session->active) = 1;
 287         CMM_ACCESS_ONCE(session->been_active) = 1;
 288
 289         session->statedump_pending = 1;
 290         lttng_ust_sockinfo_session_enabled(session->owner);
 291 end:
 292         return ret;
 293 }
 294
 295 int lttng_session_disable(struct lttng_session *session)
 296 {
 297         int ret = 0;
 298
 299         if (!session->active) {
 300                 ret = -EBUSY;
 301                 goto end;
 302         }
 303         /* Set atomically the state to "inactive" */
 304         CMM_ACCESS_ONCE(session->active) = 0;
 305
 306         /* Set transient enabler state to "disabled" */
 307         session->tstate = 0;
 308         lttng_session_sync_enablers(session);
 309 end:
 310         return ret;
 311 }
 312
 313 int lttng_channel_enable(struct lttng_channel *channel)
 314 {
 315         int ret = 0;
 316
 317         if (channel->enabled) {
 318                 ret = -EBUSY;
 319                 goto end;
 320         }
 321         /* Set transient enabler state to "enabled" */
 322         channel->tstate = 1;
 323         lttng_session_sync_enablers(channel->session);
 324         /* Set atomically the state to "enabled" */
 325         CMM_ACCESS_ONCE(channel->enabled) = 1;
 326 end:
 327         return ret;
 328 }
 329
 330 int lttng_channel_disable(struct lttng_channel *channel)
 331 {
 332         int ret = 0;
 333
 334         if (!channel->enabled) {
 335                 ret = -EBUSY;
 336                 goto end;
 337         }
 338         /* Set atomically the state to "disabled" */
 339         CMM_ACCESS_ONCE(channel->enabled) = 0;
 340         /* Set transient enabler state to "enabled" */
 341         channel->tstate = 0;
 342         lttng_session_sync_enablers(channel->session);
 343 end:
 344         return ret;
 345 }
 346
 347 /*
 348  * Supports event creation while tracing session is active.
 349  */
 350 static
 351 int lttng_event_create(const struct lttng_event_desc *desc,
 352                 struct lttng_channel *chan)
 353 {
 354         const char *event_name = desc->name;
 355         struct lttng_event *event;
 356         struct lttng_session *session = chan->session;
 357         struct cds_hlist_head *head;
 358         struct cds_hlist_node *node;
 359         int ret = 0;
 360         size_t name_len = strlen(event_name);
 361         uint32_t hash;
 362         int notify_socket, loglevel;
 363         const char *uri;
 364
 365         hash = jhash(event_name, name_len, 0);
 366         head = &chan->session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 367         cds_hlist_for_each_entry(event, node, head, hlist) {
 368                 assert(event->desc);
 369                 if (!strncmp(event->desc->name, desc->name,
 370                                         LTTNG_UST_SYM_NAME_LEN - 1)
 371                                 && chan == event->chan) {
 372                         ret = -EEXIST;
 373                         goto exist;
 374                 }
 375         }
 376
 377         notify_socket = lttng_get_notify_socket(session->owner);
 378         if (notify_socket < 0) {
 379                 ret = notify_socket;
 380                 goto socket_error;
 381         }
 382
 383         /*
 384          * Check if loglevel match. Refuse to connect event if not.
 385          */
 386         event = zmalloc(sizeof(struct lttng_event));
 387         if (!event) {
 388                 ret = -ENOMEM;
 389                 goto cache_error;
 390         }
 391         event->chan = chan;
 392
 393         /* Event will be enabled by enabler sync. */
 394         event->enabled = 0;
 395         event->registered = 0;
 396         CDS_INIT_LIST_HEAD(&event->bytecode_runtime_head);
 397         CDS_INIT_LIST_HEAD(&event->enablers_ref_head);
 398         event->desc = desc;
 399
 400         if (desc->loglevel)
 401                 loglevel = *(*event->desc->loglevel);
 402         else
 403                 loglevel = TRACE_DEFAULT;
 404         if (desc->u.ext.model_emf_uri)
 405                 uri = *(desc->u.ext.model_emf_uri);
 406         else
 407                 uri = NULL;
 408
 409         /* Fetch event ID from sessiond */
 410         ret = ustcomm_register_event(notify_socket,
 411                 session->objd,
 412                 chan->objd,
 413                 event_name,
 414                 loglevel,
 415                 desc->signature,
 416                 desc->nr_fields,
 417                 desc->fields,
 418                 uri,
 419                 &event->id);
 420         if (ret < 0) {
 421                 DBG("Error (%d) registering event to sessiond", ret);
 422                 goto sessiond_register_error;
 423         }
 424
 425         /* Populate lttng_event structure before tracepoint registration. */
 426         cmm_smp_wmb();
 427         cds_list_add(&event->node, &chan->session->events_head);
 428         cds_hlist_add_head(&event->hlist, head);
 429         return 0;
 430
 431 sessiond_register_error:
 432         free(event);
 433 cache_error:
 434 socket_error:
 435 exist:
 436         return ret;
 437 }
 438
 439 static
 440 int lttng_desc_match_wildcard_enabler(const struct lttng_event_desc *desc,
 441                 struct lttng_enabler *enabler)
 442 {
 443         int loglevel = 0;
 444         unsigned int has_loglevel = 0;
 445
 446         assert(enabler->type == LTTNG_ENABLER_WILDCARD);
 447         /* Compare excluding final '*' */
 448         if (strncmp(desc->name, enabler->event_param.name,
 449                         strlen(enabler->event_param.name) - 1))
 450                 return 0;
 451         if (desc->loglevel) {
 452                 loglevel = *(*desc->loglevel);
 453                 has_loglevel = 1;
 454         }
 455         if (!lttng_loglevel_match(loglevel,
 456                         has_loglevel,
 457                         enabler->event_param.loglevel_type,
 458                         enabler->event_param.loglevel))
 459                 return 0;
 460         return 1;
 461 }
 462
 463 static
 464 int lttng_desc_match_event_enabler(const struct lttng_event_desc *desc,
 465                 struct lttng_enabler *enabler)
 466 {
 467         int loglevel = 0;
 468         unsigned int has_loglevel = 0;
 469
 470         assert(enabler->type == LTTNG_ENABLER_EVENT);
 471         if (strcmp(desc->name, enabler->event_param.name))
 472                 return 0;
 473         if (desc->loglevel) {
 474                 loglevel = *(*desc->loglevel);
 475                 has_loglevel = 1;
 476         }
 477         if (!lttng_loglevel_match(loglevel,
 478                         has_loglevel,
 479                         enabler->event_param.loglevel_type,
 480                         enabler->event_param.loglevel))
 481                 return 0;
 482         return 1;
 483 }
 484
 485 static
 486 int lttng_desc_match_enabler(const struct lttng_event_desc *desc,
 487                 struct lttng_enabler *enabler)
 488 {
 489         struct lttng_ust_excluder_node *excluder;
 490
 491         /* If event matches with an excluder, return 'does not match' */
 492         cds_list_for_each_entry(excluder, &enabler->excluder_head, node) {
 493                 int count;
 494
 495                 for (count = 0; count < excluder->excluder.count; count++) {
 496                         int found, len;
 497                         char *excluder_name;
 498
 499                         excluder_name = (char *) (excluder->excluder.names)
 500                                         + count * LTTNG_UST_SYM_NAME_LEN;
 501                         len = strnlen(excluder_name, LTTNG_UST_SYM_NAME_LEN);
 502                         if (len > 0 && excluder_name[len - 1] == '*') {
 503                                 found = !strncmp(desc->name, excluder_name,
 504                                                 len - 1);
 505                         } else {
 506                                 found = !strncmp(desc->name, excluder_name,
 507                                                 LTTNG_UST_SYM_NAME_LEN - 1);
 508                         }
 509                         if (found) {
 510                                 return 0;
 511                         }
 512                 }
 513         }
 514         switch (enabler->type) {
 515         case LTTNG_ENABLER_WILDCARD:
 516                 return lttng_desc_match_wildcard_enabler(desc, enabler);
 517         case LTTNG_ENABLER_EVENT:
 518                 return lttng_desc_match_event_enabler(desc, enabler);
 519         default:
 520                 return -EINVAL;
 521         }
 522 }
 523
 524 static
 525 int lttng_event_match_enabler(struct lttng_event *event,
 526                 struct lttng_enabler *enabler)
 527 {
 528         if (lttng_desc_match_enabler(event->desc, enabler)
 529                         && event->chan == enabler->chan)
 530                 return 1;
 531         else
 532                 return 0;
 533 }
 534
 535 static
 536 struct lttng_enabler_ref * lttng_event_enabler_ref(struct lttng_event *event,
 537                 struct lttng_enabler *enabler)
 538 {
 539         struct lttng_enabler_ref *enabler_ref;
 540
 541         cds_list_for_each_entry(enabler_ref,
 542                         &event->enablers_ref_head, node) {
 543                 if (enabler_ref->ref == enabler)
 544                         return enabler_ref;
 545         }
 546         return NULL;
 547 }
 548
 549 /*
 550  * Create struct lttng_event if it is missing and present in the list of
 551  * tracepoint probes.
 552  */
 553 static
 554 void lttng_create_event_if_missing(struct lttng_enabler *enabler)
 555 {
 556         struct lttng_session *session = enabler->chan->session;
 557         struct lttng_probe_desc *probe_desc;
 558         const struct lttng_event_desc *desc;
 559         struct lttng_event *event;
 560         int i;
 561         struct cds_list_head *probe_list;
 562
 563         probe_list = lttng_get_probe_list_head();
 564         /*
 565          * For each probe event, if we find that a probe event matches
 566          * our enabler, create an associated lttng_event if not
 567          * already present.
 568          */
 569         cds_list_for_each_entry(probe_desc, probe_list, head) {
 570                 for (i = 0; i < probe_desc->nr_events; i++) {
 571                         int found = 0, ret;
 572                         struct cds_hlist_head *head;
 573                         struct cds_hlist_node *node;
 574                         const char *event_name;
 575                         size_t name_len;
 576                         uint32_t hash;
 577
 578                         desc = probe_desc->event_desc[i];
 579                         if (!lttng_desc_match_enabler(desc, enabler))
 580                                 continue;
 581                         event_name = desc->name;
 582                         name_len = strlen(event_name);
 583
 584                         /*
 585                          * Check if already created.
 586                          */
 587                         hash = jhash(event_name, name_len, 0);
 588                         head = &session->events_ht.table[hash & (LTTNG_UST_EVENT_HT_SIZE - 1)];
 589                         cds_hlist_for_each_entry(event, node, head, hlist) {
 590                                 if (event->desc == desc
 591                                                 && event->chan == enabler->chan)
 592                                         found = 1;
 593                         }
 594                         if (found)
 595                                 continue;
 596
 597                         /*
 598                          * We need to create an event for this
 599                          * event probe.
 600                          */
 601                         ret = lttng_event_create(probe_desc->event_desc[i],
 602                                         enabler->chan);
 603                         if (ret) {
 604                                 DBG("Unable to create event %s, error %d\n",
 605                                         probe_desc->event_desc[i]->name, ret);
 606                         }
 607                 }
 608         }
 609 }
 610
 611 /*
 612  * Create events associated with an enabler (if not already present),
 613  * and add backward reference from the event to the enabler.
 614  */
 615 static
 616 int lttng_enabler_ref_events(struct lttng_enabler *enabler)
 617 {
 618         struct lttng_session *session = enabler->chan->session;
 619         struct lttng_event *event;
 620
 621         /* First ensure that probe events are created for this enabler. */
 622         lttng_create_event_if_missing(enabler);
 623
 624         /* For each event matching enabler in session event list. */
 625         cds_list_for_each_entry(event, &session->events_head, node) {
 626                 struct lttng_enabler_ref *enabler_ref;
 627
 628                 if (!lttng_event_match_enabler(event, enabler))
 629                         continue;
 630
 631                 enabler_ref = lttng_event_enabler_ref(event, enabler);
 632                 if (!enabler_ref) {
 633                         /*
 634                          * If no backward ref, create it.
 635                          * Add backward ref from event to enabler.
 636                          */
 637                         enabler_ref = zmalloc(sizeof(*enabler_ref));
 638                         if (!enabler_ref)
 639                                 return -ENOMEM;
 640                         enabler_ref->ref = enabler;
 641                         cds_list_add(&enabler_ref->node,
 642                                 &event->enablers_ref_head);
 643                 }
 644
 645                 /*
 646                  * Link filter bytecodes if not linked yet.
 647                  */
 648                 lttng_enabler_event_link_bytecode(event, enabler);
 649
 650                 /* TODO: merge event context. */
 651         }
 652         return 0;
 653 }
 654
 655 /*
 656  * Called at library load: connect the probe on all enablers matching
 657  * this event.
 658  * Called with session mutex held.
 659  */
 660 int lttng_fix_pending_events(void)
 661 {
 662         struct lttng_session *session;
 663
 664         cds_list_for_each_entry(session, &sessions, node) {
 665                 lttng_session_lazy_sync_enablers(session);
 666         }
 667         return 0;
 668 }
 669
 670 /*
 671  * For each session of the owner thread, execute pending statedump.
 672  * Only dump state for the sessions owned by the caller thread, because
 673  * we don't keep ust_lock across the entire iteration.
 674  */
 675 void lttng_handle_pending_statedump(void *owner)
 676 {
 677         struct lttng_session *session;
 678
 679         /* Execute state dump */
 680         lttng_ust_baddr_statedump(owner);
 681
 682         /* Clear pending state dump */
 683         if (ust_lock()) {
 684                 goto end;
 685         }
 686         cds_list_for_each_entry(session, &sessions, node) {
 687                 if (session->owner != owner)
 688                         continue;
 689                 if (!session->statedump_pending)
 690                         continue;
 691                 session->statedump_pending = 0;
 692         }
 693 end:
 694         ust_unlock();
 695         return;
 696 }
 697
 698 /*
 699  * Only used internally at session destruction.
 700  */
 701 static
 702 void _lttng_event_destroy(struct lttng_event *event)
 703 {
 704         struct lttng_enabler_ref *enabler_ref, *tmp_enabler_ref;
 705
 706         cds_list_del(&event->node);
 707         lttng_destroy_context(event->ctx);
 708         lttng_free_event_filter_runtime(event);
 709         /* Free event enabler refs */
 710         cds_list_for_each_entry_safe(enabler_ref, tmp_enabler_ref,
 711                         &event->enablers_ref_head, node)
 712                 free(enabler_ref);
 713         free(event);
 714 }
 715
 716 void lttng_ust_events_exit(void)
 717 {
 718         struct lttng_session *session, *tmpsession;
 719
 720         cds_list_for_each_entry_safe(session, tmpsession, &sessions, node)
 721                 lttng_session_destroy(session);
 722 }
 723
 724 /*
 725  * Enabler management.
 726  */
 727 struct lttng_enabler *lttng_enabler_create(enum lttng_enabler_type type,
 728                 struct lttng_ust_event *event_param,
 729                 struct lttng_channel *chan)
 730 {
 731         struct lttng_enabler *enabler;
 732
 733         enabler = zmalloc(sizeof(*enabler));
 734         if (!enabler)
 735                 return NULL;
 736         enabler->type = type;
 737         CDS_INIT_LIST_HEAD(&enabler->filter_bytecode_head);
 738         CDS_INIT_LIST_HEAD(&enabler->excluder_head);
 739         memcpy(&enabler->event_param, event_param,
 740                 sizeof(enabler->event_param));
 741         enabler->chan = chan;
 742         /* ctx left NULL */
 743         enabler->enabled = 1;
 744         cds_list_add(&enabler->node, &enabler->chan->session->enablers_head);
 745         lttng_session_lazy_sync_enablers(enabler->chan->session);
 746         return enabler;
 747 }
 748
 749 int lttng_enabler_enable(struct lttng_enabler *enabler)
 750 {
 751         enabler->enabled = 1;
 752         lttng_session_lazy_sync_enablers(enabler->chan->session);
 753         return 0;
 754 }
 755
 756 int lttng_enabler_disable(struct lttng_enabler *enabler)
 757 {
 758         enabler->enabled = 0;
 759         lttng_session_lazy_sync_enablers(enabler->chan->session);
 760         return 0;
 761 }
 762
 763 int lttng_enabler_attach_bytecode(struct lttng_enabler *enabler,
 764                 struct lttng_ust_filter_bytecode_node *bytecode)
 765 {
 766         bytecode->enabler = enabler;
 767         cds_list_add_tail(&bytecode->node, &enabler->filter_bytecode_head);
 768         lttng_session_lazy_sync_enablers(enabler->chan->session);
 769         return 0;
 770 }
 771
 772 int lttng_enabler_attach_exclusion(struct lttng_enabler *enabler,
 773                 struct lttng_ust_excluder_node *excluder)
 774 {
 775         excluder->enabler = enabler;
 776         cds_list_add_tail(&excluder->node, &enabler->excluder_head);
 777         lttng_session_lazy_sync_enablers(enabler->chan->session);
 778         return 0;
 779 }
 780
 781 int lttng_attach_context(struct lttng_ust_context *context_param,
 782                 struct lttng_ctx **ctx, struct lttng_session *session)
 783 {
 784         /*
 785          * We cannot attach a context after trace has been started for a
 786          * session because the metadata does not allow expressing this
 787          * information outside of the original channel scope.
 788          */
 789         if (session->been_active)
 790                 return -EPERM;
 791
 792         switch (context_param->ctx) {
 793         case LTTNG_UST_CONTEXT_PTHREAD_ID:
 794                 return lttng_add_pthread_id_to_ctx(ctx);
 795         case LTTNG_UST_CONTEXT_VTID:
 796                 return lttng_add_vtid_to_ctx(ctx);
 797         case LTTNG_UST_CONTEXT_VPID:
 798                 return lttng_add_vpid_to_ctx(ctx);
 799         case LTTNG_UST_CONTEXT_PROCNAME:
 800                 return lttng_add_procname_to_ctx(ctx);
 801         case LTTNG_UST_CONTEXT_IP:
 802                 return lttng_add_ip_to_ctx(ctx);
 803         default:
 804                 return -EINVAL;
 805         }
 806 }
 807
 808 int lttng_enabler_attach_context(struct lttng_enabler *enabler,
 809                 struct lttng_ust_context *context_param)
 810 {
 811 #if 0   // disabled for now.
 812         struct lttng_session *session = enabler->chan->session;
 813         int ret;
 814
 815         ret = lttng_attach_context(context_param, &enabler->ctx,
 816                         session);
 817         if (ret)
 818                 return ret;
 819         lttng_session_lazy_sync_enablers(enabler->chan->session);
 820 #endif
 821         return -ENOSYS;
 822 }
 823
 824 static
 825 void lttng_enabler_destroy(struct lttng_enabler *enabler)
 826 {
 827         struct lttng_ust_filter_bytecode_node *filter_node, *tmp_filter_node;
 828         struct lttng_ust_excluder_node *excluder_node, *tmp_excluder_node;
 829
 830         /* Destroy filter bytecode */
 831         cds_list_for_each_entry_safe(filter_node, tmp_filter_node,
 832                         &enabler->filter_bytecode_head, node) {
 833                 free(filter_node);
 834         }
 835
 836         /* Destroy excluders */
 837         cds_list_for_each_entry_safe(excluder_node, tmp_excluder_node,
 838                         &enabler->excluder_head, node) {
 839                 free(excluder_node);
 840         }
 841
 842         /* Destroy contexts */
 843         lttng_destroy_context(enabler->ctx);
 844
 845         cds_list_del(&enabler->node);
 846         free(enabler);
 847 }
 848
 849 /*
 850  * lttng_session_sync_enablers should be called just before starting a
 851  * session.
 852  */
 853 static
 854 void lttng_session_sync_enablers(struct lttng_session *session)
 855 {
 856         struct lttng_enabler *enabler;
 857         struct lttng_event *event;
 858
 859         cds_list_for_each_entry(enabler, &session->enablers_head, node)
 860                 lttng_enabler_ref_events(enabler);
 861         /*
 862          * For each event, if at least one of its enablers is enabled,
 863          * and its channel and session transient states are enabled, we
 864          * enable the event, else we disable it.
 865          */
 866         cds_list_for_each_entry(event, &session->events_head, node) {
 867                 struct lttng_enabler_ref *enabler_ref;
 868                 struct lttng_bytecode_runtime *runtime;
 869                 int enabled = 0, has_enablers_without_bytecode = 0;
 870
 871                 /* Enable events */
 872                 cds_list_for_each_entry(enabler_ref,
 873                                 &event->enablers_ref_head, node) {
 874                         if (enabler_ref->ref->enabled) {
 875                                 enabled = 1;
 876                                 break;
 877                         }
 878                 }
 879                 /*
 880                  * Enabled state is based on union of enablers, with
 881                  * intesection of session and channel transient enable
 882                  * states.
 883                  */
 884                 enabled = enabled && session->tstate && event->chan->tstate;
 885
 886                 CMM_STORE_SHARED(event->enabled, enabled);
 887                 /*
 888                  * Sync tracepoint registration with event enabled
 889                  * state.
 890                  */
 891                 if (enabled) {
 892                         if (!event->registered)
 893                                 register_event(event);
 894                 } else {
 895                         if (event->registered)
 896                                 unregister_event(event);
 897                 }
 898
 899                 /* Check if has enablers without bytecode enabled */
 900                 cds_list_for_each_entry(enabler_ref,
 901                                 &event->enablers_ref_head, node) {
 902                         if (enabler_ref->ref->enabled
 903                                         && cds_list_empty(&enabler_ref->ref->filter_bytecode_head)) {
 904                                 has_enablers_without_bytecode = 1;
 905                                 break;
 906                         }
 907                 }
 908                 event->has_enablers_without_bytecode =
 909                         has_enablers_without_bytecode;
 910
 911                 /* Enable filters */
 912                 cds_list_for_each_entry(runtime,
 913                                 &event->bytecode_runtime_head, node) {
 914                         lttng_filter_sync_state(runtime);
 915                 }
 916         }
 917 }
 918
 919 /*
 920  * Apply enablers to session events, adding events to session if need
 921  * be. It is required after each modification applied to an active
 922  * session, and right before session "start".
 923  * "lazy" sync means we only sync if required.
 924  */
 925 static
 926 void lttng_session_lazy_sync_enablers(struct lttng_session *session)
 927 {
 928         /* We can skip if session is not active */
 929         if (!session->active)
 930                 return;
 931         lttng_session_sync_enablers(session);
 932 }